1. Field of the Invention
The present invention relates to structural improvements in a battery charger for use with portable telephone and, more particularly, to structural improvements in a battery charger which may tap both household and onboard vehicle power outlets and which is used in conjunction with portable telephone.
2. Description of the Related Art
The ultimate objective of communication is obviously to transmit or exchange ideas and information to or with anyone or any entity wherever and whenever desired. That objective has been pursued traditionally by capabilities of communication between fixed points and more recently by means of mobile communication. Mobile communication refers to the communication between fixed-point subscriber and business telephone sets on the one hand, and such mobile entities as vessels, vehicles, aircraft and the people on board these means of transportation. Recent years have seen the appreciable growth in the field of portable telephone, one of the preferred modes of mobile communication.
Portable communication equipment including portable telephone sets operates generally on batteries which are charged by battery chargers. Because of their use in conjunction with the portable equipment, the battery chargers should preferably tap both the commercial household power outlet and the onboard vehicle battery outlet.
Traditionally, the household outlet-based battery charger and the onboard vehicle power outlet-based battery charger have been manufactured as separate devices. The primary reason for this is that the battery charger for use on board the vehicle, requiring various protective circuits for protecting the device from such severe ambient conditions as vibration, is too expensive for parallel use with the household outlet.
FIG. 1 is a perspective view of the prior art household outlet-based battery charger proposed by this applicant, the charger being shown to accommodate a portable telephone set and its backup battery pack. In FIG. 1, a household outlet-based battery charger 1 has a prop-up side 8 against which a portable telephone set is placed at a predetermined angle relative to the perpendicular direction. The battery charger 1 also has a concave portion 9 in which to insert the backup battery pack. Reference numeral 6 is a portable telephone set equipped with the battery pack. To be charged, the portable telephone set 6 is propped against the prop-up side 8 of the battery charger 1 as indicated by arrow A.
The backup battery back 7 is inserted in the concave portion 9 as indicated by arrow B while being charged. At one end of a cord 2 is a connector 5 that attaches to the battery charger 1. The other end of the cord 2 is equipped with an AC/DC adapter that is plugged into a commercial household outlet 4. In this manner, the battery charger 1 charges both the portable telephone set 6 and its backup battery pack 7 at the same time.
Unlike onboard vehicle power outlet-based battery chargers, the household outlet-based battery charger generally is not subject to vibration. It follows that no special structure is needed to keep the portable telephone set and its battery pack in place during charging. For this reason, in the prior art charger structure, the portable telephone set is simply propped against the prop-up side of the charger and the battery pack inserted where designated, as illustrated in FIG. 1. The battery charger of this type is not suitable for use on board the vehicle for reasons primarily attributable to the vibration and impact from the running vehicle. One reason for inappropriateness for onboard use is that the vibration or impact may dislodge the portable telephone set and its battery pack from the battery charger and cause poor or disrupted connections of charge-related terminals, making the charging operation impossible. Another reason is that the vibration or impact may erroneously reset the battery charger, causing the battery to be overcharged and bringing it to a premature end of its service life.